Voltage stability enhancement during excess load increments through optimal location of UPFC devices

Modern power systems are subjected to widespread line failures due to excess load demands, leading to voltage instability and voltage collapse. The objective of this paper is to study the application of Unified Power Flow Controller (UPFC) devices in improving voltage profile and controlling the power flowing through the transmission lines during excess load increments. Voltage Stability Analysis of the network is carried out by computing the eigen values of the power system reduced Jacobian matrix for each case of load increments before and after placing the UPFC device in the system. The line outage for which we get maximum number of critical eigen values is termed as the critical line outage. Voltage Stability Index is computed for each line corresponding to this critical outage. The line which has got the highest VSI for the critical outage is called as the critical line which indicates the optimal location of UPFC device. After placing the UPFC device on the critical line, the voltage magnitudes of the severely affected buses for this critical load increments is compared with those magnitudes during the critical outage.. The proposed approach is demonstrated on the IEEE 14 bus system in Matlab PSAT( Power system analysis Toolbox) software. The results obtained shows that UPFC devices improves the voltage profile of the buses and controls both active and reactive power flows across the transmission lines thus, preventing their outages during excess load demands and making the power system network voltage stable.